Resveratrol, which is a member of polyphenols contained in the skin of grapes, for example, is known as an antioxidant component. Resveratrol has also been reported to have physiological functions such as lifespan-extending, anti-cancer, and anti-microbial effects in various living organisms. Further, resveratrol has a melanogenesis suppressing effect, and thus, use of resveratrol in whitening cosmetics has been proposed (Patent Literature 1 and Non-Patent Literatures 1 and 2, for example). Since resveratrol has various functionalities as described above, resveratrol is now increasingly used not only in cosmetic products and foods but also in pharmaceuticals.
On the other hand, resveratrol has a problem in pharmaceutical formulation in that it is poorly soluble in water, and also has extremely poor stability. Thus, derivatization of resveratrol has previously been proposed to improve the water solubility and stability of resveratrol.
Patent Literature 2, for example, reported that β-glucosides (in particular, resveratrol 3-O-β-glucoside) of resveratrol exhibit increased water solubility and stability compared to resveratrol. While it is known that resveratrol 3O-β-glucoside exhibits a water solubility approximately 10-fold higher than that of resveratrol (Non-Patent Literature 3), it only has a water solubility of approximately 400 μg/mL. Thus, further improvement in water solubility is still desired. Moreover, resveratrol 3-O-β-glucoside has been reported to be inferior in tyrosinase inhibitory effect to resveratrol (Non-Patent Literatures 1 and 2), and thus, is also unsatisfactory in functionality.
Patent Literature 3 discloses that the use of resveratrol ethers such as resveratrol glucoside can improve the instability of resveratrol. Patent Literature 3 describes that resveratrol glucoside can be obtained by extraction from polygonum cuspidatum tissue or in vitro cultures of vitis vinifera cells. The resveratrol glucoside obtained by all of these methods is resveratrol 3-O-β-glucoside. The resveratrol glucoside disclosed in Patent Literature 3 is therefore also unsatisfactory in water solubility and functionality, as described above.
The resveratrol derivatives obtained in the conventional art are therefore still unsatisfactory in water solubility and functionality, although they have improved stability.
On the other hand, Non-Patent Literature 4 discloses obtaining resveratrol 3-O-α-glucoside through interaction of a solution containing resveratrol and sucrose with cells of Streptococus mutans. Non-Patent Literature 4, however, nowhere discusses the physical properties or characteristics of resveratrol 3-O-α-glucoside. It is known that generally in a glycoside, the physical properties and function of the aglycone per se are greatly affected by the bonded position or form of the sugar. Thus, Non-Patent Literature 4, which fails to disclose the physical properties or characteristics of resveratrol 3-O-α-glucoside, cannot be said to show applicability of resveratrol 3-O-α-glucoside.
Further, commercial production of products containing a resveratrol derivative will require using a concentrate of the resveratrol derivative as a raw material to be added. Resveratrol derivatives, however, have low water solubility, and the conventional art has not established a technique of concentrating a resveratrol derivative in a dissolved state to a high concentration. Thus, there is also a problem in that a resveratrol derivative cannot be prepared in the form of a concentrate.
In the modern society, consumers' growing interest in beauty has led to an increasing number of people who desire to maintain a healthy and youthful skin, regardless of age or sex. In the fields of cosmetic products, foods, medicines, and the like, therefore, the development of products for preventing skin aging such as spots, dullness, wrinkles, and sags is actively ongoing. In recent years, however, the consumer demand for performance in terms of skin aging prevention has continued increasing, and there is a need for the development of a novel anti-skin aging agent that can meet this consumer demand.